It is known in the art to manufacture cartons for different types of contents through the use of methods and machines which convert packing material carton blanks to finished cartons that are filled with the desired contents and then closed. A carton blank is typically utilized as the starting point for the manufacture of the finished cartons. The carton blank includes first, second, third and fourth side wall panels, which form the side walls of the finished carton. Extending from the first, second, third and fourth side wall panels are first, second, third and fourth bottom panels, respectively. As will be described in more detail below, the bottom panels are appropriately folded and sealed to form the bottom end wall of the finished carton. At the opposite end of each of the side wall panels is a top panel, the details of which are known and will not be described here as they do not form a specific part of the present invention.
Before the cartons can be filled with the desired contents, it is necessary to fold and seal the bottom panels to form a sealed bottom end wall. There are known types of apparatus for forming and sealing the bottom end wall of carton blanks such as the one described above. A more detailed discussion of the features of the apparatus, as well as features of the machine that result in the filling and closing of the carton top, is set forth in U.S. Pat. No. 3,785,113 and U.S. Pat. No.4,790,123, the disclosures of which are incorporated herein by reference.
Generally speaking, carton blanks that have been formed into a generally tubular form with a substantially square cross-section are placed on feeders that comprise a continuous feeder conveyor. The feeder conveyor transports the generally tubular carton blanks to a rotatable mandrel assembly which is comprised of a plurality of radially outwardly directed mandrels. Two side-by-side feeders which each transport carton blanks to a respective rotatable mandrel assembly can be used. It is, of course, to be understood that a single feeder or more than two feeders could be employed, each of which conveys carton blanks to a respective rotatable mandrel assembly.
After a carton blank has been conveyed to the mandrel assembly and received on a respective one of the mandrels, the mandrel assembly rotates and causes the carton blank to rotate through a series of stations. As described in more detail in the aforementioned U.S. patents, a carton blank (not shown) is initially received on the mandrel from the feeder conveyor at an in-feed station. Thereafter, the mandrel is indexed one station to a heating station at which the bottom panels of the carton blank are heated by a suitable heating device. The heating device can take the form of an apparatus that directs hot air at the bottom panels. The mandrel is then indexed to the next station where the bottom panels are sealed by a suitable sealing device to form a sealed bottom end wall of the carton. While rotating from the heating station to the sealing station, the bottom panels can be subjected to a folding operation so that when the carton blank reaches the sealing station, the bottom panels can be sealed in the proper manner. A further indexing of the mandrel from the sealing station moves the carton blank to a cooling station where the sealed bottom end wall is cooled by a suitable cooling device. As an alternative to a cooling device, the bottom panels can be cooled by the surrounding ambient air. One final indexing of the mandrel causes the carton with a sealed bottom end wall to be placed on a feeder conveyor where it is intermittently advanced to various processing stations such as a filling station for filling the carton with contents and a top end closing station where the top end of the carton is closed and sealed.
Through use of a carton blank similar to that described above and an apparatus similar to that described above, the resulting sealed bottom end wall of the carton obtains a particular configuration. As seen from the carton interior, the second and fourth bottom panels are located inwardly of the first and third bottom panels with respect to the interior of the carton. Also, the first bottom panel overlaps a portion of the outer surface of the third bottom panel. Further, a portion of the edge of the third bottom panel located between the second and fourth bottom panels is exposed to the interior of the carton.
It has been found that the exposure of a portion of the edge of the third bottom panel to the interior is somewhat problematic. That is, over time, the contents in the carton tend to infiltrate the exposed edge portion of the third bottom panel, possibly causing delamination of the packing material. As a result, contamination of the carton contents may occur.
To address that problem, the carton blank described above has been modified slightly. In particular, as seen in FIG. 1, the carton blank 20 is provided with a bottom panel flap 35 that extends from the third bottom panel 34. A crease line 37 is also provided for facilitating folding of the bottom panel flap 35. During the folding operation, the bottom panel flap 35 is folded outwardly away from the first bottom panel 30 and back upon the third bottom panel 34 along the crease line 37. When the bottom panels 30, 32, 34 36 are sealed, the bottom panel flap 35 is positioned between the first bottom panel 30 and the third bottom panel 34 as illustrated in FIG. 10. In that way, an edge portion of the third bottom panel 34 is not exposed to the interior of the carton between the second and fourth bottom panels 32, 36.
In an attempt to ensure proper folding of the bottom panel flap 35, a prefolding arrangement has been provided for prefolding the bottom panel flap 35. Such a prefolding arrangement is illustrated in FIG. 2 which depicts the forward end of the feeder conveyor 40 relative to the mandrel 42 which receives the carton blank 20. The prefolding arrangement includes a carrier 52 that is mounted on the feeder conveyor 40. The carton 20 blank is positioned on the feeder conveyor 40 in front of the carrier 52, and the carrier 52 follows the carton blank 20 as it moves along the feeder conveyor 40. A fixedly mounted prefolding block 54 is also provided. The prefolding block 54 is positioned at the forward end of the feeder conveyor 40 and just in front of the position that the mandrel 42 assumes at the in-feed station for receiving the carton blank 20.
As the carton blank 20 is received on the mandrel 42, the carrier 52 begins to move downwardly as a result of the course of movement of the feeder conveyor 40. The prefolding block 54 is positioned relative to the carrier 52 such that as the carrier 52 passes by the prefolding block 54, a small clearance space is provided between the tip of the carrier 52 and the tip of the prefolding block 54. As the carrier 52 moves downwardly, it catches the bottom panel flap 35 and bends the bottom panel flap 35 around the tip of the prefolding block 54, thereby prefolding the bottom panel flap 35. Further movement of the feeder conveyor 40 moves the carrier 52 out of the way, whereupon the mandrel 42 indexes upwardly from the position illustrated in FIG. 2 to the heating station.
After the bottom panels have been heated at the heating station, the mandrel 42 is indexed to move the carton blank with the heated bottom panels towards the sealing station. To ensure that the bottom panels are properly folded before being sealed, the bottom panels are preferably brought into engagement with a bottom panel folding apparatus similar to that illustrated in FIG. 3 as the carton blank 20 is proceeding from the heating station to the sealing station.
The bottom panel folding apparatus includes a tuck folder 56 secured to a mounting arm 58, and a bending unit 62 which is also secured to the mounting arm 58. The mounting arm 58 is connected to a rotatably driven shaft 66, and encircling the shaft 66 is a shaft housing 65 that houses bearings for the shaft 66. The shaft housing 65 is mounted on a frame structure 68. Consequently, rotation of the shaft 66 results in rotation of the mounting arm 58 and consequently, rotation of the tuck folder 56 and the bending unit 62.
As can be seen from FIG. 3, the bending unit 62 includes a straight portion 62' which is positioned perpendicular to the mounting arm 58 and a curved portion 62" that curves toward the tuck folder 56. Also, mounted at the distal free end of the tuck folder 56 is a roller 57.
The bottom panel folding apparatus also includes two folding fingers 60 (only one of which can be seen in FIG. 3) and a guide 64. As best illustrated in FIGS. 4 and 6, each of the folding fingers 60 includes an outwardly projecting contacting pin 70. The folding fingers 60 and the guide 64 are stationarily mounted on the frame structure 68 so that they do not rotate with the mounting arm 58. However, each of the folding fingers 60 is rotatably driven about its longitudinal axis 60'.
In operation, the folding fingers 60 continually rotate about their respective longitudinal axes 60'. The system is designed such that the rotation of the folding fingers 60, the rotation of the shaft 66, and the rotation of the mandrel 42 are all synchronized with one another. Since the details of the apparatus which allow that synchronized movement is known to persons in the art and does not form a specific part of the present invention, a description is not included here.
As the mandrel 42 rotates in the direction of the arrow A shown in FIG. 5 from the heating station to the sealing station, the shaft 66 rotates in the counterclockwise direction represented by the arrow B in FIG. 5. The synchronized rotation of the mandrel 42, the shaft 66 and the folding fingers 60 is such that the contacting pins 70 on the rotating folding fingers 60 come into contact with the second and fourth bottom panels 32, 36 of the carton blank 20 while the mandrel 42 is rotating as seen in FIGS. 4 and 6. As a result, the second and fourth bottom walls 32, 36 begin to fold inwardly.
At about the same time, the rotating mounting arm 58 has rotated to such an extent that the roller 57 on the tuck folder 56 comes into contact with the third bottom panel 34, thereby causing the third bottom panel 34 to begin folding inwardly towards the first bottom panel 30 as seen in FIG. 5. Because the mandrel 42 is rotating, the first bottom panel 30 of the carton blank 20 is brought into contact with the stationary guide 64 as illustrated in FIG. 5. That causes the first bottom panel 30 to begin folding inwardly towards the third bottom panel 34. Further, the rear surface 63 of the bending unit 62 and the bottom panel flap 35 are brought into contact with one another which causes the bottom panel flap 35 to fold outwardly away from the first bottom panel 30 as also shown in FIG. 9. The outward folding of the bottom panel flap 35 is also facilitated in some respects by the earlier prefolding that was imparted to the bottom panel flap 35 at the in-feed station.
The continued rotation of the mandrel 42 in the direction of the arrow A in FIG. 5, in combination with the continued rotation of the mounting arm 58 in the direction of the arrow B in FIG. 5 and the continued rotation of the folding fingers 60 about their axes 60' results in substantial completion of the folding of the bottom panels. That is, the inward folding of the second and fourth bottom panels 32, 36 is substantially completed through continued rotation of the folding fingers 60. The synchronized rotation of the folding fingers 60 and the mandrel 42 helps ensure that when the mandrel 42, and thus the carton blank 20, have reached a certain point, the folding fingers 60 have rotated out of the way so that the contacting pins 70 do not interfere with further rotation of the mandrel and the carton blank 20. Likewise, continued rotation of the mounting arm 58 and the mandrel 42 substantially completes the inward folding of the third bottom panel 34, and the outward folding of the bottom panel flap 35.
Once the tuck folder 56 and the bending unit 62 have rotated out of the way, continued rotation of the mandrel 42 completes the folding of the first bottom panel 30 as a result of the contact between the stationary guide 64 and the first bottom panel 30. In that regard, the first bottom panel 30 is actually forced down onto the underlying bottom panels 32, 34, 36 and the bottom panel flap 35 by way of the guide 64. Thus, the final folding of the first bottom panel 30 completes the folding of the remaining bottom panels 32, 34, 36 and the bottom panel flap 35.
After the bottom panels have been folded, further rotation of the mandrel 42 advances the carton blank 20 to the sealing station where the bottom panels are sealed to form a bottom end wall of the carton. After sealing, the bottom end wall of the carton is formed such that the second and fourth bottom panels 32, 36 are located inwardly of the first and third bottom panels 30, 34 with respect to the interior of the carton. Further, the first bottom panel 30 overlaps a portion of the outwardly facing surface of the third bottom panel 34, and the bottom panel flap 35 is positioned between the third bottom panel 34 and the first bottom panel 30.
While useful in achieving folding of the carton blank shown in FIG. 1, the combination of the prefolding assembly shown in FIG. 2 and described above, and the bottom panel folding apparatus illustrated in FIGS. 3-6 and described above is susceptible of certain improvements. For example, with reference to FIG. 2, it has been found to be somewhat difficult to maintain precise tolerances with respect to the position of the bottom panel flap 35 relative to the carrier 52 and the prefolding block 54. As a result, it is not always possible to ensure that the crease line 37 about which the bottom panel flap 35 is to be folded is located precisely at the tip of the prefolding block 54. Consequently, it sometimes happens that the bottom panel flap 35 is prefolded about a line other than the crease line 37. As might be expected, such an improper prefolding of the bottom panel flap 35 can cause problems later on during the bottom folding step. For example, when the bottom panel flap 35 and the bending unit 62 are brought into contact with one another, the bottom panel flap 35 may tend to fold at two places-- the crease line 37 and the crease formed by the improper prefolding of the bottom panel flap 35.
With reference to FIG. 3, another area of improvement involves the bending unit 62 that is employed to fold the bottom panel flap 35 outwardly upon the bottom panel 34. As seen in FIG. 5, when the mounting arm 58 is rotating in the direction of arrow B, the rear curved surface 63 at the distal free end of the bending unit 62 that contacts the bottom panel flap 35 is actually moving away from the bottom panel flap 35. That means that the force applied to the bottom panel flap 35 by the bending unit 62 may not be as effective as necessary to ensure that the bottom panel flap 35 is properly folded when the first bottom panel 30 forces the bottom panel flap 35 downwardly. More specifically, it has been found that the bending unit 62 releases the bottom panel flap 35 much too soon and as a result, there is too long a period of time in which the bottom panel flap 35 can move forwardly before being contacted by the inwardly and downwardly folding first bottom panel 30. Consequently, the bottom panel flap 35 may fold back towards the first bottom panel 30. If the bottom panel flap 35 folds back towards the first bottom panel 30 too far, the bottom panel flap 35 may not be properly folded when contacted by the first bottom panel 30.